Copolyesters of a polymethylene glycol, a dimeric fatty acid and an aromatic dicarboxylic acid are known, as exemplified for instance in U.S. Pat. Nos. 3,383,343 and 3,954,689. Such copolyesters have been suggested for various purposes including manufacture of elastomeric filaments and other elastomeric products such as tires, hose, wire coverings, etc. More specifically, the above mentioned patents suggest broadly elastomeric copolyesters containing from about 31 to about 65 weight percent (wt%) based on the copolyester of dimeric fatty acid.
Polybutylene terephthalate (PBT) reinforced with thermally stable reinforcing fibers such as glass fibers is well known as a molding resin and is described in numerous patents and publications including for instance U.S. Pat. Nos. 3,814,725, 3,814,786 and 3,624,024. Fiber reinforcement generally improves the tensile strength, flexural strength, flexural modulus and heat deflection temperature of the molding composition. However, moldings of fiber reinforced PBT frequently have less than desirable impact resistance for many applications.